What is the maximum duration a secondary system must operate a protected premise under quiescent load?

The maximum duration a secondary system must operate a protected premise under quiescent load is 24 hours. This is a standard requirement intended to ensure that in the event of a primary system failure, there is sufficient backup to maintain operations and safety for a reasonable period.

Having a 24-hour operational capability under quiescent load allows for sufficient time to respond to issues such as power outages or equipment malfunctions. This duration is critical for emergency preparedness, ensuring that essential functions continue without interruption during power loss.

While longer durations might seem beneficial in some contexts, they can also lead to increased costs and complexity in system design and operation. The 24-hour requirement strikes a balance between reliability and practicality, providing a robust safety net without overwhelming infrastructure needs.